People rely on disposable absorbent products to help participate in and enjoy their daily activities.
Disposable absorbent products, including adult incontinence articles, feminine pads, dressings for wounds, and diapers, are generally manufactured by combining several components. These components typically include a liquid-permeable topsheet; a liquid-impermeable backsheet attached to the topsheet; and an absorbent core located between the topsheet and the backsheet. When the disposable article is worn, the liquid-permeable topsheet is positioned next to the body of the wearer and allows passage of bodily fluids into the absorbent core. The liquid-impermeable backsheet helps prevent leakage of fluids held in the absorbent core. The absorbent core is designed to have desirable physical properties, e.g. a high absorbent capacity and high absorption rate, so that bodily fluids can be transported from the skin of the wearer into the disposable absorbent product. Often the absorbent core includes fluff pulp, typically cellulosic in nature, to help achieve these properties.
Fluff pulp is usually formed by unwinding a rolled-up sheet of substantially dry fiber and directing the free end of the sheet to a hammermill. The hammermill typically has rapidly moving metal bars that repeatedly impact, tear, and break the free end of the sheet into individual fibers or fiber aggregates. These individual fibers, fiber aggregates, and other optional materials are then put into a stream of air that is directed to a moving wire; i.e., an airlaid process. The air passes through the wire, but most of the fibers, fiber aggregates, and any optional materials are retained at the surface of the wire to form a fibrous web. This fibrous web is then incorporated into the disposable absorbent product. By adjusting the rate at which the rolled sheet of substantially dry fiber is unwound and fed into a hammermill, a manufacturer can meter the fluff pulp to the airlaid process so that the input of fluff pulp approximates or matches the output of fluff pulp as incorporated into the final product. This method of processing and metering fluff pulp works, but a rolled sheet of dry fiber is generally more expensive than some other forms of dry fiber. For example, flash-dried bales of fiber cost significantly less than roll-form pulp. Flash-dried bales are currently used in wetlaid processes for forming a fibrous web, not the airlaid process described above. In a typical wetlaid process, water and flash-dried bales of fiber are put into a tank having rotating blades. The action of the blades, and the absorption of water by fibers, breaks the bale apart into an aqueous slurry of substantially individual fibers. The aqueous slurry is then directed to a moving wire where the water drains through the wire but fibers are retained on the surface of the wire.
What is needed is a method and apparatus for breaking apart bales of fiber into substantially dry, individual fibers or fiber aggregates, i.e. dry fluff, and metering the dry fluff to a hopper or other receptacle, or other process, such as an airlaid process for use in making disposable absorbent articles.
The present invention is directed to an apparatus and method that satisfy this need. One version of an apparatus having features of the present invention includes: a bale support member for supporting a bale of pulp, the bale support member defining two openings; two fiberizing assemblies, each having a disrupting-element support member attached to a rotatable shaft; for each fiberizing assembly, a plurality of disrupting elements attached to and extending outwardly from the disrupting-element support member a distance, generally adjustable, sufficient to allow a portion of the disrupting elements to protrude through an opening to contact a surface layer of the bale of pulp, the surface layer having a dimension parallel to the longitudinal axis of the disrupting-element support member, each disrupting element extending longitudinally and substantially continuously along the disrupting-element support member for a distance of about 100% or more of said surface-layer dimension; a transportation assembly for moving the bale of pulp back and forth along the bale support member and over the openings so that the disrupting elements contact a surface layer in the bale to form substantially dry, individual fibers and fiber aggregates, i.e. dry fluff; an adjustable reciprocating assembly attached to and providing a motive force for moving the transportation assembly, the adjustable reciprocating assembly permitting adjustment of the frequency by which the transportation assembly moves back and forth over the opening, the frequency being adjustable from about 1 sec [stroke]xe2x88x921 to about 50 sec [stroke]xe2x88x921, and more specifically from about 3 sec [stroke]xe2x88x921 to about 35 sec [stroke]xe2x88x921; and a conduction assembly for conducting the dry fluff to a hopper or other receptacle, or another process such as an airlaid process. In some versions of the invention, the apparatus comprises one slot and one or more fiberizing assemblies, or more than two slots and/or two fiberizing assemblies.
One version of an apparatus in which dry fluff is formed from a bale and metered at a desired rate to another process, such as an airlaid process, comprises: a sensor for determining a value S1 corresponding to the amount of dry fluff being used by the other process per unit time; a transmitter for transmitting a value M1 corresponding to the value S1 to a reciprocation frequency controller having instructions for correlating the value M1 to a value R1, the value R1 corresponding to a reciprocation frequency; and a reciprocation frequency controller for operably controlling the adjustable reciprocation assembly to the reciprocation frequency corresponding to the value R1 so that the amount of dry fluff formed per unit time corresponds to the amount of dry fluff being used by the other process per unit time.
Another version of an apparatus in which dry fluff is formed from a bale and metered at a desired rate to another process, such as an airlaid process, comprises: a measurement device for determining the amount of dry fluff being used by the other process per unit time; and a controlling device for force-adjusting the reciprocation frequency to a frequency such that the amount of dry fluff formed per unit time corresponds to the amount of dry fluff being used by the other process per unit time.
One version of a method of fiberizing a bale of pulp into dry fluff and metering the dry fluff to a hopper or other receptacle, or another process, such as an airlaid process, includes the steps of: providing a bale of pulp having a density of about 0.5 g cmxe2x88x923 or greater, specifically about 0.7 g cmxe2x88x923 or greater, and more specifically about 0.9 g cmxe2x88x923 or greater; conveying the bale of pulp to a bale support member so that the bale rests on the bale support member, the support member defining two openings through which disrupting elements protrude; moving the bale of pulp back and forth at an adjustable frequency over the openings so that the disrupting elements, which extend outwardly from disrupting-element support members attached to rotatable shafts, contact a surface layer in the bale of pulp to form dry fluff; selecting a frequency corresponding to a desired amount of dry fluff formed per unit time, for example the amount of dry fluff required to operate another process, such as an airlaid process, per unit time; and conducting the amount of dry fluff formed per unit time to a hopper or other receptacle, or another process such as an airlaid process.
In another version of a method of the present invention, the dry fluff that is formed has a percent-fiberization value of at least about 50%, specifically at least about 75%, particularly at least about 85%, and more particularly at least about 90%.
One version of a method in which dry fiber is formed from a bale and metered at a desired rate to another process, such as an airlaid process, comprises the steps of: sensing a value S1 corresponding to the amount of dry fluff being used by another process per unit time; transmitting a value M1 corresponding to the value S1 to a reciprocation frequency controller, the reciprocation frequency controller having instructions for correlating the value M1 to a value R1, the value R1 corresponding to a reciprocation frequency; using the controller to operably control the adjustable reciprocation assembly to the reciprocation frequency corresponding to the value R1 so that the amount of dry fluff formed per unit time corresponds to the amount of dry fluff being used by the other process per unit time.
Another version of a method in which dry fluff is formed from a bale and metered at a desired rate to another process, such as an airlaid process, comprises the steps of: determining the amount of dry fluff being used by the other process per unit time; and force-adjusting the reciprocation frequency to a frequency such that the amount of dry fluff formed per unit time corresponds to the amount of dry fluff being used by the other process per unit time.
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.